Smoking article having carbon dioxide delivery technology for sensorially improved carbon filtration and method of making

ABSTRACT

Provided is a smoking article including a filter, tobacco, and a carbon dioxide charge. The carbon dioxide charge provides increased levels of carbon dioxide during smoking to enhance the taste and sensorial smoking experience.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. provisional Application No. 60/935,543, filed on Aug. 17, 2007, the entire content of which is incorporated herein by reference.

SUMMARY

Provided is a smoking article comprising tobacco, a filter and a charge of carbon dioxide gas. The charge of carbon dioxide gas provides at least about 10% more carbon dioxide on average for all puffs than a traditional cigarette so as to improve the taste of mainstream smoke.

Also provided is a method of making a cigarette having elevated levels of carbon dioxide in mainstream smoke.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cigarette charged with carbon dioxide.

FIG. 2 is a graph comparing the carbon dioxide levels during the initial puffs of the smoking article charged with carbon dioxide of FIG. 1 and a traditional cigarette

FIGS. 3A and 3B are perspective views of preferred embodiments of a smoking article charged with carbon dioxide and including a carbon molecular sieve.

FIG. 4 is a graph showing the amount of carbon dioxide in the first puff of a smoking article based on the amount of carbon molecular sieve present in the smoking article and the amount of carbon dioxide on average in all puffs based on the amount of carbon molecular sieve present in the filter.

FIG. 5 is a graph showing the concentration of carbon dioxide in the first through seventh puffs of a smoking article including carbon on tow and a smoking article including carbon on tow, a carbon molecular sieve, and a charge of carbon dioxide.

FIG. 6 is a perspective view of a preferred embodiment of a smoking article having a filter including tubes containing carbon dioxide and a sorbent.

FIG. 7 is an illustration of the hollow tubes of FIG. 6.

FIG. 8 is a perspective view of a hollow tube shown in FIGS. 6 and 7.

FIG. 9 is front view of an embodiment of a package for containing the smoking articles of FIGS. 1, 3 and 6.

FIG. 10 is a top view of the package of FIG. 9.

FIG. 11 is a graph showing the effect of the carbon dioxide charge on smoke chemistry.

DETAILED DESCRIPTION

As used herein, the term “smoking articles” is intended to include elongated smoking articles, such as cigarettes and cigars. Non-traditional cigarettes such as cigarettes for electrical smoking systems as described in commonly-assigned U.S. Pat. Nos. 6,026,820; 5,988,176; 5,915,387; 5,692,526; 5,692,525; 5,666,976; 5,345,951; 4,991,606; 4,966,171 and 5,499,636, the disclosures of which are hereby incorporated by reference herein in their entireties, are also included in the definition of smoking articles or cigarettes generally.

As used herein, the term “traditional cigarette” describes filtered, preferably low tar, cigarettes including a sorbent that do not carry a carbon dioxide charge as described herein.

As used herein, the term “smoking” is intended to include the heating, combusting or otherwise causing release of mainstream smoke from tobacco.

As used herein, the term “mainstream” smoke refers to the mixture of gases passing down the smoking article and issuing through the filter end, e.g., the amount of smoke issuing or drawn from the mouth end of a cigarette during smoking of the cigarette. The mainstream smoke contains smoke that is drawn in through both the lighted region, as well as through the cigarette paper wrapper. The term “side stream” smoke refers to smoke produced during static burning.

As used herein, the term “initial puffs” refers to the first, second, third and/or fourth puffs taken after lighting and/or heating a cigarette or smoking article.

As used herein, the term “all puffs” refers to all puffs taken during the use of a smoking article.

As used herein, the term “sorption” includes filtration by absorption and/or adsorption. Sorption encompasses interactions on the outer surface of the sorbent, as well as interactions within the pores and channels of the sorbent. Sorption also describes the loading of carbon dioxide on a carbon molecular sieve.

As used herein, the term “sorbent” refers to a substance that can condense or hold molecules of other substances on its surface, and/or can take up other substances, i.e., through penetration of the other substances into its inner structure, or into its pores. Accordingly, the term “sorbent” as used herein refers to either an adsorbent, an absorbent, or a substance that can function as both an adsorbent and an absorbent.

As used herein, the term “remove” refers to adsorption and/or absorption of at least some portion of at least one constituent of mainstream smoke.

As used herein, the terms “carbon dioxide charge,” “charge of carbon dioxide,” and “charged” refers to the addition of and a supply of carbon dioxide in a smoking article component. The charge of carbon dioxide can be added by passing carbon dioxide through the smoking article and/or filter or by incorporating a carbon dioxide filled tube or other such container that sealingly retains carbon dioxide at ambient temperature and/or pressure within the filter. The terms “charge” and “charging” also refer to the act of passing carbon dioxide through and/or supplying carbon dioxide to the smoking article and/or filter.

Provided is a smoking article having a charge of carbon dioxide so as to increase the amount of carbon dioxide in mainstream smoke during smoking of the smoking article, thereby enhancing the flavor thereof.

The carbon dioxide provides a “mouthfeel” effect similar to that of a carbonated soda (in contrast to a flat soda), thereby improving the taste of the smoking article. In addition, carbon dioxide adsorbed on a carbon adsorbent can reduce the initial activity of the carbon adsorbent, due to the blocking of the smallest micropores, thereby preventing the removal of some aroma compounds. In theory, the loading of carbon dioxide on activated carbon and/or a carbon molecular sieve in a filter may reduce the “carbon taste” some American smokers associate with carbon filtration.

Preferably, the smoking article provides at least about 10% more carbon dioxide on average in all puffs than a traditional cigarette, and more preferably at least about 20% more carbon dioxide on average in all puffs, (e.g. at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 100%). Also preferably, the smoking article provides at least about 25% more carbon dioxide in the initial puffs as compared to a traditional cigarette.

As described herein and shown in FIG. 1, a smoking article 10 includes a filter 12, a tobacco rod 14, and a charge of carbon dioxide. Preferably, the filter 12 includes a first filter segment 16 and a sorbent 18. Also preferably, the sorbent is in the form of carbon on tow (COT) 18. In an embodiment, the sorbent is a carbon molecular sieve in the form of beads, granules, pellets, carbon molecular sieve on tow, and the like. The filter 12 is joined to the tobacco rod 14 by tipping paper 22.

In an embodiment, as shown in FIGS. 1, 3A and 3B, a ventilation zone 8 is established with a first row (and optionally second and possibly third rows) of ventilation holes through the tipping paper 22. Preferably, the ventilation zone 8 achieves a ventilation level of the smoking article of at least 25% and more preferably at least 50% to 90%.

In a preferred embodiment, the charge of carbon dioxide can be introduced into the smoking article by attaching a smoking article to a gas line with a flexible rubber septa and then passing 100% carbon dioxide gas into and through the smoking article 10 and/or filter 12 for at least about one minute, and more preferably at least about 2 minutes, prior to packaging so as to provide a charge of carbon dioxide in the smoking article which increases the amount of carbon dioxide in mainstream smoke at least during the initial puffs of the smoking article. Preferably, about 0.05 liters per minute (L/min) to about 2.5 L/min, more preferably about 0.25 L/min to about 1.0 L/min of carbon dioxide is passed through the smoking article and/or filter. Preferably, the smoking article is placed in a sealed container immediately after charging the smoking article with carbon dioxide to thereby retain the elevated carbon dioxide level charged into the smoking article until release during smoking.

In a preferred embodiment, the carbon dioxide is stored on the carbon-on-tow filter material (COT) while in the sealed container to thereby avoid the carbon on tow releasing the carbon dioxide under atmospheric pressure and/or temperature conditions.

FIG. 2 is a graph comparing the carbon dioxide concentration of the initial puffs of the smoking article of FIG. 1, charged with carbon dioxide, and a traditional filtered smoking article when tested under Federal Trade Commission (FTC) conditions (35 cc per 2 seconds) on a standard smoking machine. As shown, the first and second puffs of the smoking article of FIG. 1 have a higher concentration of carbon dioxide as compared to the traditional cigarette indicating better flavor in the first and second puffs. Despite the presence of the sorbent in the charged smoking article, which can act to remove flavor compounds, the carbon dioxide charge increases the amount of carbon dioxide at least in the initial puffs thereby enhancing the flavor of the initial puffs.

Exemplary sorbents for use in the filter 12 include molecular sieves such as zeolites (e.g. Type 4A, 13X, etc.), silicas, silicates (e.g. aluminosilicates), aluminas, carbon molecular sieves and/or carbons (e.g. activated carbon). Preferably, the filter includes about 30 mg to about 250 mg of the sorbent.

By “activated carbon” is meant any porous, high surface area form of carbon. Activated carbon can be derived via thermal treatment of any suitable carbon source. The activation treatment typically increases the porosity, and activated carbon can be provided with a wide range of pore sizes or the pore sizes can be controlled to provided a desired pore size distribution.

In a preferred embodiment, the activated carbon can be in the form of beads, granules, fibers, pellets, carbon on tow, carbon paper, and the like.

Preferably, activated carbon can have any desired pore size distribution that comprises pores such as micropores, mesopores and macropores. The term “microporous” generally refers to such materials having pore sizes of about 20 Angstroms or less while the term “mesoporous” generally refers to such materials with pore sizes of about 20 Angstroms to about 500 Angstroms.

Preferably, the activated carbon is adapted to adsorb constituents of mainstream smoke, particularly, those of the gas phase including aldehydes, ketones and other volatile organic compounds, and in particular 1,3-butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, styrene, acetaldehyde and hydrogen cyanide.

Since a sorbent, such as activated carbon, may also absorb the flavor compounds, a charge of carbon dioxide is added to the filter to increase the amount of carbon dioxide in the initial puffs of the smoking article, thereby enhancing the flavor thereof.

In an embodiment, the sorbent is a carbon molecular sieve. Because a carbon molecular sieve has a smaller average pore size with a narrow distribution as compared to activated carbon, the carbon molecular sieve does not adsorb constituents of mainstream smoke as effectively as the activated carbon, but is suitable for adsorption and storage of small molecules such as carbon dioxide.

Examples of suitable types of tobacco materials that can be used in the tobacco rod 14 of the smoking article 10 include, but are not limited to, flue-cured tobacco, Burley tobacco, Maryland tobacco, Oriental tobacco, rare tobacco, specialty tobacco, blends thereof and the like. The tobacco material may be provided in any suitable form, including, but not limited to, tobacco lamina, processed tobacco materials, aged tobacco such as volume expanded or puffed tobacco, processed tobacco stems, such as cut-rolled or cut-puffed stems, reconstituted tobacco materials, blends thereof, and the like. Tobacco substitutes may also be used.

Preferably, the tobacco is normally used in the form of cut filler, i.e., in the form of shreds or strands cut into widths ranging from about 2 mm to about 1 mm or even about 0.5 mm. The lengths of the strands range from between about 5 mm to about 80 mm. An exemplary cigarette can include between about 300 mg and about 750 mg of tobacco, preferably around 550 mg for a standard cigarette. The cigarettes may further comprise one or more flavors, or suitable diluents (e.g., burn diluents, combustion modifying agents, coloring agents, binders, etc.).

Referring now to FIG. 3A, in a preferred embodiment, the smoking article 10 includes a filter 12, a tobacco rod 14, and a carbon dioxide charge. Preferably, the filter includes a first filter segment 16, located at the downstream end of the smoking article 10, a first sorbent 18 and a second sorbent 25 that is capable of absorbing and retaining carbon dioxide prior to use, and also capable of releasing carbon dioxide due to the force of a puff. Also preferably, heating and/or burning the smoking article aids in the release of the carbon dioxide from the second sorbent.

To avoid release of carbon dioxide into the atmosphere, the smoking article 10 is preferably stored in a sealed container immediately after charging the smoking article 10 with carbon dioxide so as to maintain the carbon dioxide levels in the smoking article 10. For example, a smoking article 10 left at atmospheric temperature and pressure for about 5 minutes loses about 40% of the carbon dioxide charge. Thus, in a preferred embodiment, the smoking article 10 is stored in a sealed container within 5 minutes of charging a sorbent in the smoking article with carbon dioxide, and more preferably within about 2 minutes to about 3 minutes of loading the sorbent with carbon dioxide.

Also preferably, the smoking article 10 remains in a sealed container until use. Preferably, the smoking article 10 is used within 1 minute to about 10 minutes of removing the smoking article 10 from the sealed container. Otherwise, the carbon dioxide loaded on the sorbent is released into the atmosphere.

In a preferred embodiment, the second sorbent 25 occupies a cavity between sections of the first sorbent 18, which is preferably carbon on tow (COT) and/or a carbon molecular sieve in the form of beads, pellets, granules, carbon molecular sieve on tow and the like. Preferably, the smoking article 10 is charged with carbon dioxide prior to packaging so that the average carbon dioxide level at least in the initial puffs is higher than that of a traditional cigarette by at least about 10%.

In a preferred embodiment, the filter 12 is attached to the tobacco rod 14 by a tipping paper 22, which preferably circumscribes both the entire length of the filter 12 and an adjacent region of the tobacco rod 14. The tipping paper 22 is typically a paper like product; however, any suitable material can be used.

In an embodiment, the cavity holding the second sorbent 25 may be taped with an adhesive on overtipping paper 19 having low gas permeability to slow the release of the carbon dioxide charge from the second sorbent. The overtipping paper 19 circumscribes a portion of COT plugs 18 on either side of the cavity. Preferably, a ventilation zone 8 is upstream and/or downstream of the cavity, but does not overlap the cavity.

In a preferred embodiment, the second sorbent 25 includes a carbon molecular sieve material, such as high density carbon beads, granules, pellets, carbon molecular sieve-on-tow and the like, having an average particle size of about 1 mm, and fine micropores, such as the carbon molecular sieve available from SKC Inc. or the carbon molecular sieve described in U.S. Pat. No. 4,820,681, the entire content of which is incorporated herein by reference. In a preferred embodiment, the filter 14 includes at least about 20 mg of carbon molecular sieve, more preferably at least about 50 mg.

In an embodiment, as shown in FIG. 3B, in addition to the first filter segment 16, the filter may include an additional filter segment 11 upstream of the carbon molecular sieve 25. Preferably, the first filter segment 16 and the optional upstream filter segment 11 are made of cellulose acetate tow having a low resistance to draw (“RTD”). However, any suitable filtering material can be used.

As shown in FIG. 4, a graph shows the carbon dioxide content in a first puff and the average carbon dioxide content in all puffs as a function of various amounts of carbon molecular sieve present in the filter. As shown, the amount of carbon dioxide released rises in relation to the amount of carbon molecular sieve present in the filter indicating that the carbon molecular sieve aids in retaining the carbon dioxide in the smoking article prior to use, but effectively releases the carbon dioxide due to the force of a puff. The inclusion of carbon molecular sieve in the filter results in a higher concentration of carbon dioxide in at least the initial puffs, and preferably for all puffs, which in turn improves the flavor thereof.

Not wishing to be bound by theory, the increase in carbon dioxide is believed to be due to the ability of the carbon molecular sieve to absorb the carbon dioxide when the smoking article is charged, and also to the ability of the carbon molecular sieve to release the carbon dioxide due to the force of a puff. In a preferred embodiment, the carbon molecular sieve material dried to less than about 2% water content is loaded with carbon dioxide under ambient temperature and pressure conditions. For example, a gram of carbon molecular sieve material can be loaded with 70 mg to 80 mg of carbon dioxide.

Referring now to FIG. 5, a cigarette including 90 mg of carbon on tow, 100 mg carbon molecular sieve and a carbon dioxide charge are smoked on a standard smoking machine under Federal Trade Commission (FTC) conditions (35 cc per 2 seconds) and compared to a traditional cigarette containing 120 mg of carbon on tow and not charged with carbon dioxide. As shown, the carbon dioxide levels of the initial puffs are higher for the cigarette containing 100 mg carbon molecular sieve and charged with carbon dioxide indicating enhanced flavor in the initial puffs.

Referring now to FIG. 6, in a preferred embodiment, a smoking article 10 in the form of a cigarette includes a filter 12, a tobacco rod 14, and a carbon dioxide charge. Preferably, the filter 12 includes a first sorbent 18 and a second sorbent 25 that is capable of absorbing and retaining carbon dioxide prior to use, and also capable of releasing the carbon dioxide when a puff is taken. Preferably, the second sorbent 25 and the charge of carbon dioxide are contained in at least one hollow tube 30. In an embodiment, a charge of carbon dioxide may also be contained in the first sorbent 18. In a preferred embodiment, the first sorbent 18 is in the form of carbon on tow that surrounds the one or more hollow tubes 30.

In a preferred embodiment, the hollow tube 30 is a permeable, semi-permeable, and/or impermeable tube 30 within the filter 12. Preferably, each of the one or more hollow tubes 30 is sealed by a seal 31 (shown in FIG. 8) that breaks due to the force of a puff. In a preferred embodiment, the seal 31 is preferably used to immobilize the contents of the hollow tubes 30, and thus reduce dissipation of the charge of carbon dioxide and/or the carbon molecular sieve until the seal 31 is broken, ruptured, or perforated.

Preferably, the seal 31 is a frangible material, such as a polymer, which is capable of both sealing the hollow tube 30, as well as breaking, rupturing, and/or perforating on demand. Preferably, the seal 31 is designed to break when smoke is drawn through the filter. Also preferably, the seal 31 is made of sugar or pectin, which can also be provided to flavor filtrate, such as smoke filtrate, contacting the seal 31 if desired. A single seal 31 can be used to seal the downstream ends of multiple tubes 30 and another single seal 31 can be used to seal upstream ends of the tubes 30, as shown in FIG. 8.

Preferably, the hollow tubes 30 are oriented in a direction in which smokes travels through the smoking article so that the smoke can pass through the lumens of the tubes 30 to contact the sorbent 25 and release the charge of carbon dioxide contained therein.

As shown in FIG. 7, in an embodiment, the hollow tubes 30 are approximately parallel to one another in order to allow the smoke to evenly penetrate the hollow tubes 30.

Preferably, the hollow tubes 30 are sized to a length less than the length of the filter 12 so that the entire length of each of the hollow tubes 30 can fit within the area of the filter 12 as the hollow tubes 30 are aligned in the direction of the smoke flow.

Also preferably, the inner diameter of the hollow tubes 30 is about 0.5 mm to about 3.0 mm. In a preferred embodiment, the filter 12 includes 1 to 10 hollow tubes 30 (e.g., 1 to 3, 3 to 5, 5 to 7 or 7 to 10).

In a preferred embodiment, the hollow tube 30 is charged by first sealing the second sorbent 25 in the tube 30 and then charging the tube 30 and the second sorbent 25 with carbon dioxide through a slow diffusion process. Preferably, most of the charge of carbon dioxide will be absorbed by the second sorbent 25, and the remainder of the charge will fill the tube 30. In another embodiment, the tubes 30 containing the second sorbent 25 are charged with carbon dioxide and then sealed with a seal 31 in a carbon dioxide atmosphere.

Smoking articles having carbon dioxide in one or more sealed tubes or other sealed arrangement can be packaged with conventional packaging materials.

In an embodiment, a smoking article 10 charged with carbon dioxide is placed in a sealed container, such as the container shown in FIGS. 9 and 10. Preferably, the container 50 has multiple compartments 52, each sized and configured to hold and sealingly retain one smoking article 10 therein. In a preferred embodiment, flavorants can be inserted into the compartments 52 of the container. In an embodiment, each compartment 52 may be charged with carbon dioxide prior to sealing a smoking article 10 including a first and/or second sorbent therein. Preferably, each compartment 52 is charged with 100% carbon dioxide gas. Preferably, a seal 65 contains the smoking article and/or carbon dioxide charge within each compartment 52.

In an embodiment, each smoking article 10 can be individually wrapped and/or inserted in a conventional cigarette pack.

Table 1 shows the effect of the addition of a carbon molecular sieve on ventilation (VENT), resistance to draw (RTD), and total particulate matter (TPM), as well as the average amount of carbon dioxide in all puffs of a smoking article, as compared to a cigarette containing 120 mg COT.

TABLE 1 Average RTD, TPM, CO2, CO2 delivery Sample Vent, % mm mg % vol increase, % Cigarette 48 113 5.7 3.9 — containing 120 mg COT only Cigarette 44 120 6.5 6.9 77 (increase as containing 90 mg compared to the COT and 100 mg cigarette carbon molecular containing 120 mg sieve and charged COT only) with carbon dioxide

As shown in Table 1, the delivery of carbon dioxide per cigarette containing 90 mg carbon on tow and 100 mg of carbon dioxide charged carbon molecular sieve increased about 77% on average for all puffs as compared to a cigarette including only 120 mg carbon on tow. In addition, the ventilation and RTD is similar to that of the cigarette not including the carbon molecular sieve, suggesting that the carbon molecular sieve does not significantly affect smoke chemistry, but does enhance the delivery of carbon dioxide.

In addition, as shown in FIG. 11, the addition of the carbon molecular sieve resulted in the reduction of more gas constituents as compared to traditional cigarettes including 120 mg of carbon on tow. For example, the presence of the carbon molecular sieve reduces the amount of acetaldehyde, isoprene, and carbonyl sulfide despite the inability of carbon molecular sieve to adsorb constituents of mainstream smoke as effectively as activated carbon.

Also provided herein is a method of making a smoking article having increased carbon dioxide delivery technology so as to improve the taste of the initial puffs.

It will be understood that the foregoing description is of the preferred embodiments, and is, therefore, merely representative of the article and methods of manufacturing the same. It can be appreciated that variations and modifications of the different embodiments in light of the above teachings will be readily apparent to those skilled in the art. Accordingly, the exemplary embodiments, as well as alternative embodiments, may be made without departing from the spirit and scope of the articles and methods as set forth in the attached claims. 

We claim:
 1. A smoking article comprising: tobacco; a filter; and a charge of carbon dioxide gas, wherein said charge of carbon dioxide gas provides at least about 10% more carbon dioxide on average for all puffs than a traditional cigarette so as to improve the taste thereof.
 2. The smoking article of claim 1, wherein said filter includes a first sorbent and/or a second sorbent and wherein said first sorbent and/or said second sorbent is loaded with carbon dioxide.
 3. The smoking article of claim 2, wherein the second sorbent is a carbon molecular sieve.
 4. The smoking article of claim 3, wherein said carbon molecular sieve is in the form of pellets, granules, carbon molecular sieve-on-tow and/or beads.
 5. The smoking article of claim 2, wherein said first sorbent is a molecular sieve, selected from zeolites, silicas, silicates, aluminas, carbon molecular sieve, and/or activated carbon.
 6. The smoking article of claim 5, wherein said activated carbon is in the form of carbon on tow, beads, pellets, granules, fibers, and/or dust.
 7. The smoking article of claim 1, wherein said filter includes a mouthend filter segment and wherein said mouthend filter segment is cellulose acetate.
 8. The smoking article of claim 2, wherein said second sorbent is contained in at least one hollow tube and/or a cavity and wherein said at least one hollow tube is impermeable, semi-permeable, and/or permeable and includes at least one frangible seal.
 9. The smoking article of claim 8, wherein said at least one hollow tube is impermeable and includes at least one frangible seal.
 10. The smoking article of claim 8, wherein said at least one hollow tube comprises a plurality of hollow tubes with upstream and downstream ends, each of the tubes surrounded by the first sorbent and includes at least one frangible seal at the upstream and downstream ends so as to retain said carbon dioxide within said at least one hollow tube.
 11. The smoking article of claim 8, wherein said seal is about 0.001 mm to about 1.0 mm thick and wherein said seal is made of a polymer.
 12. A filter for a smoking article comprising: a downstream filter segment; and an upstream charge of carbon dioxide gas.
 13. The filter of claim 12, wherein said filter includes a first sorbent and/or a second sorbent and wherein said upstream charge of carbon dioxide gas is contained in said first sorbent and/or said second sorbent.
 14. The filter of claim 13, wherein said first sorbent is carbon-on-tow and said second sorbent is a carbon molecular sieve.
 15. A method of making a smoking article charged with carbon dioxide comprising: attaching a tobacco rod to a filter to form a smoking article; and charging said smoking article with carbon dioxide to form a carbon dioxide charged smoking article.
 16. The method of claim 15, wherein said smoking article is charged with 100% carbon dioxide gas for at least about 1 minute by attaching the smoking article to a gas line with a flexible septa and passing carbon dioxide through the smoking article at a rate of at least about 0.5 liters per minute and wherein said carbon dioxide charged smoking article is placed in a container and sealed therein within about 5 minutes of charging said smoking article with carbon dioxide.
 17. The method of claim 15, wherein said smoking article is charged with carbon dioxide by incorporating a tube containing carbon dioxide and/or a carbon molecular sieve loaded with carbon dioxide in the filter, the tube having a frangible seal which releases carbon dioxide into mainstream smoke during smoking of the tobacco rod. 